Planar electroluminescent plural character display



Dec..1, 1970 A.J.M lNTYRE I 9 PLANAR ELECTROLUMINESCENT PLURAL CHARACTER DISPLAY Filed May 24, 1968 2 Sheets-Sheet 1 GWSTQZT 6M9 CW5 FIG? M/VENTO/i ALFRED J. MAC INTYRE Wv/M 'A r TORNEY Dec 1 3 3 A. J. Ma m'ryR:

- 3,544,990 PLANAR ELECTROLUMINESCENT PLURAL CHARACTER DISPLAY Filed nay 24,- l968 2 Sheets-Sheet 2 FIGES 4 INVENTOR MAC INTYRE .4 TTOR/VEY United States Patent O 3,544,990 PLANAR ELECTROLUMINESCENT PLURAL CHARACTER DISPLAY Alfred J. MacIntyre, Nashua, N.H., assignor to Sanders Associates, Inc., Nashua, N.H., a corporation of Delaware Filed May 24, 1968, Ser. No. 731,955 Int. Cl. G08!) /22 US. Cl. 340-336 19 Claims ABSTRACT OF THE DISCLOSURE An electroluminescent display device is provided, in which the characters or multiplicity of characters, numbers and/or symbols are located within a single layer. Each character is a complete unit, and consists of a series of permanently interconnected segments which collectively form the natural shape of the character, number or symbol being displayed. Each character being a complete electrical circuit thereby requires only one external interconnecting point for applying the power to illuminate the character, number or symbol.

FIELD OF THE INVENTION This invention relates to a means for providing a visual display in which any of many predetermined display patterns, such as letters, numbers, symbols or the like can be selectively illuminated, and more particularly, to such displays in which an electroluminescent phosphor layer disposed between two electrode layers, a transparent electrode and a preformed character electrode, is excited by an electric field causing the associated phosphor area to luminesce thereby illuminating the selected character.

THE PRIOR ART In the field of electroluminescent display assemblies, it is recognized that characters such as numbers formed from seven or nine bar elements or alpha-numerics formed from fourteen bar elements may be illuminated by exciting a layer of electroluminescent phosphor between pairs of electrodes. The aforementioned bar methods result in the forming of a letter or number from a particular combination of the bar elements through the use of complex electronic gating or coding circuits. That is, when a signal is applied to the display which signifies a particular number to be illuminated, this signal must then be applied to the appropriate electrode elements. Since each electrode element operates independently of the remaining elements, each element must have its own drive circuitry.

There are many problems associated with the prior art techniques. For example, the aforementioned bar method displays the numbers, letters or characters, by necessity, in block form, a shape that is unnatural to the observer. In addition, it is possible that one of the electronic gating circuits or one of the drive circuits associated with each electrode segment will not function and the associated element will not be illuminated, thereby presenting incorrect information to the observer.

One solution to the problem has been the nixie or gas tube type display that presents script type numbers, characters and letters. However, such a device of the electroluminescent type also requires the character electrodes to be stacked in a multiple of layers which presents additional problems. The use of multiple character layers in this type of display requires that if each of the characters are to be illuminated with the same degree of brightness the applied voltage must be increased as each successive character electrode from the transparent electrode is illuminated. This means the display must be able to apply various selected voltages to the electrodes depending upon 3,544,990 Patented Dec. 1, 1970 SUMMARY OF THE INVENTION From the foregoing, it will be understood that among the objects of this invention are the following:

To provide an electroluminescent display system which requires but one stroke to form the letters, numerals or other configurations of the display;

To provide an electroluminescent display system which will not display incorrect letters or numbers because each character is independent of other characters, and each character needs but one drive circuit and no associated electronic gating circuits for illumination thereof;

To provide an electroluminescent display system which comprises a single continuous circuit path for each letter, number or character to be displayed;

To provide an electroluminescent display system in which the configuration of the character displayed forms its natural shape; 1

To provide an electroluminescent display system in which all of the characters, numbers or symbols exist in a single plane or layer.

According to this invention, these objectives are achieved by providing a character electrode unit in an electroluminescent panel which consists of a plurality of interspersed characters, letters, numbers, symbols or the like, each of which lies in the same plane. Each character is formed of a series of electrically interconnected segments, said segments collectively forming a character electrode, which when energized form the predetermined character, with each character preferably appearing in its natural shape and each character being complete unto itself. That is, each character is formed from its own individual segments with no sharing of segments between any other characters. In this manner a plurality of characters can be placed within a given area in the same plane, and when each of the characters is illuminated it appears to be located at the same physical location as the other characters.

The features of novelty which are characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental principles and to its particular embodiments, will best be understood by reference to the specifications and the accompanying drawing, in which:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an enlarged front view of a character unit of an electroluminescent device;

FIG. 2 is a section view taken along the line 2--2 in FIG. 1;

FIG. 3 is an enlarged detailed view of the number eight illustrating the segments thereof;

FIG. 4 is a schematic view of the circuit which interconnects the segments of the number eight;

FIG. 5 is a section view taken along the line 55 in FIG. 3;

FIG. 6 is an enlarged front view of a character unit with the number eight (8) illuminated;

FIG. 7 is a front view of an electroluminescent device featuring letters instead of numbers; and

FIG. 8 is a section view of an electroluminescent dislay.

P For purposes of illustration, the invention will be de-- scribed in connection with a display system which illuminates numbers. It will be understood, however, that the same principles may be employed to produce letters or other types of character configurations.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of the drawings, an electroluminescent character unit which displays a number type of presentation from zero to nine is thereby illustrated. The display device itself may have as many of these units as is deemed necessary with each unit 11 being able to display only one digit at a time. However, when a number of units 11 are joined on one display any combination of units may be illuminated. The numbers in unit 11, FIG. 1 are shown in this particular size for clarity and illustration purposes only. The actual size of the display will depend upon the requirements of the user. There is no limit to the largeness of the characters except that which is determined by physical practicalities, and the characters may be as small as desired. The limitation on the smallness of each unit display is determined by the ability of the craftsman to produce a unit 11 in which an observer can difierentiate between the numbers within a unit, and in this particular case this is a very small unit.

A close examination of the unit 11 reveals that the numbers from zero to nine are distinct and each is formed in its natural shape. That is, those characters naturally having a curvilinear shape are formed to have such a shape. Also, further inspection of the numbers reveals that each number is made up of a plurality of segments, as will be described hereinafter, with none of the segments which collectively outline one number coming in contact with a segment of any other number. In addition, each number is complete within itself; that is, none of the segments in a unit 11 are shared between two or more numbers. Accordingly, the aforementioned construction of each number permits the placement of all the numbers in a single plane thereby providing a wafer-thin electroluminescent display. Also, the numbers are placed within the same confined area. That is, the boundaries of the various numbers encompass, in part, the same area such that when each of the numbers are illuminated they appear to exist approximately in the same location.

Referring now to FIG. 2, there is further illustrated the single plane construction for the characters, where, in part, the portions of several numbers shown in FIGS. 1 and 6 are identified with the same reference numbers. From top to bottom, parts of the numbers 5, 2, 5, 6, and 2 are denoted by reference characters 11a, 11b, 11c, 11d, He, and 11 respectively with the substrate of FIG. 2 designated as 12.

To illustrate the construction of a typical number, for example the number eight, reference is hereby made to FIG. 3. As shown, the number eight is made up of a plurality of segments designated generally by the reference character 13, with the particular segments forming the number referenced by lower case letters a-j inclusive, and the spaces between the segments referenced by the lower case letters k-u inclusive. The use of the series of segments to form the number eight and each of the other characters permits the placement of all the numbers, zero to nine, within a small area and within a single plane. This particular construction of characters is made possible by electrically interconnecting the segments by electrical circuits which lie in a diflferent plane, as illustrated in FIG. 5.

Although there are many spaces between the segments that form the number eight, in the actual construction of this or any other number the physical size of the spaces between the segments is very small such that when the number is illuminated, the observer sees a solid number, and he is unaware that the number actually consists of a series of segments.

Referring now to FIG. 4, there is illustrated thereby an electrical circuit 14, employed to illuminate the number eight of FIG. 3. The electrical circuit 14 is comprised of a single signal input terminal 15, a meandering electrical circuit path 16 and a plurality of conductive pillars or lands 17. The conductive pillars 17 interconnect the electrical circuit path 16 with the character electrode segments 13 of FIG. 3, like referenced pillars connect to like referenced character electrode segments. When a discrete signal, representing the number eight, is applied to input terminal 15, that signal is coupled to the plurality of segments which collectively form the number eight. The use of one electrical circuit for the number eight, and for each of the other numbers, requires the use of but one drive circuit for each number. Also, it is this feature of the invention which eliminates gating and/0r coding circuits and associated drive circuits that are generally required for each of the individual segments in a seven, nine or fourteen element display, as mentioned hereinbefore.

Referring now to FIG. 5, there is illustrated the lands or conductive pillars 17 which integrally interconnect the electrical circuit path 16 and the character electrode segments 13. The process for providing the conductive pillars 17 is similar to that set forth with more particularity in the United States Pat. 3,374,129, issued to G. Boucher and assigned to the assignee of this application. As seen the electrical circuit path 16 is formed in a plane(s) parallel to the character electrodes 13 and is an integral part of the substrate 12 which supports the character electrode unit 11.

As seen in FIG. 1, a plurality of characters may be located within a small area. The total number of characters is without limitation so long as the illuminated characters are clearly and distinctly identifiable. The factors of clear and distinct are directly related to 1) the number of points of intersections that exist between the characters, and (2) the degree of overlap which exists between certain sections of two or more characters. For example, it is seen in FIGS. 1 and 6 that the numbers eight and three are offset from each other, otherwise there would exist a large degree of overlap and neither number, when illuminated would be clear and distinct.

The active elements of the electroluminescent panel will be but briefly discussed since they are well known in the art.

Referring now to FIG. 8, there is illustrated thereby a simplified form of an electroluminescent display device, generally indicated as 20. Adjacent to the substrate 12, which contains the character electrode segments, the electrical circuit paths 16 and the pillars 17, is a dielectric breakdown layer 21. Its composition, for example, may be barium titanate intermixed with a dielectric resin binder. A layer of electroluminescent phosphor 22 is deposited by any suitable process over the dielectric layer. A typical suitable material for the electroluminescent layer is a copper activated mixture of zinc oxide and zinc sulfide. Of course, other well known luminescent materials may be substituted therefor. Next, a second filmlike transparent, conductive electrode 23 is formed over the phosphor layer. This layer, for example may be tinoxide or stannic oxide which is coated by, for example, iridizing on a fibrous glass sheet. However, other known materials may be used. A conductor 24 is electrically connected to the transparent electrode 23 to facilitate connection thereof to an external power source. If it becomes necessary to protect the display panel from the effects of the atmosphere such as dust or moisture then the transparent electrode and surrounding area may be covered with a layer 25 of transparent epoxy or other suitable bonding material.

The terminals 15 of the electroluminescent panel which facilitate connections to external leads may be of any known design, such as pins protruding from the side of the substrate opposite the character electrodes, eyelets or tabs. The methods by which the terminals are incorporated into the display are well known. One method of forming an electroluminescent panel is set forth in a co-pending patent application of Gerald Boucher for Electroluminescent Displays Ser. No. 731,191, filed May 22, 1968 and assigned to the assignee of this application.

To illustrate this invention, the number eight is shown illuminated in FIG. 6 which figure contains the identical numerals as illustrated in outline form in FIG. 1. To illuminate the number eight a signal is applied between the input terminal 15 of the interconnecting circuit shown in FIG. 4, which is electrically coupled to all the character electrode segments 13, shown in FIG. 3, and the input terminal 24 for the transparent electrode (see FIG. 8). This voltage potential between the transparent electrode and the character electrode causes the associated electroluminescent phosphor to luminesce and illuminate the number eight. By the same procedure a voltage applied between any other character electrode and the transparent electrode will cause its respective numbers to be illuminated.

Heretofore, the description presented related only to numbers but, of course, the concept of this invention includes the display of letters or other characters which may be formed to lie in the same plane and general area. A typical type predetermined code display is illustrated in FIG. 7 and referenced generally as 18. In this particular illustration all the letters appear in 18a, and the individual letters are formed in 18b and 180 to show the segments which collectively form the letters. Accordingly, when a signal is applied to the appropriate input terminals one or any combination of the letters in FIG. 7 may be illuminated. Thus, by using the teachings revealed in relation to the numbers it is seen that many of the letters of the alphabet may be formed within a given area.

It is apparent that by extending this present concept, the display device may consist of other imaginable symbols or character configurations which lend themselves to being described in a similar fashion.

Thus, it will be appreciated from the foregoing that my electroluminescent display employing planar characters provides a reliable and relatively inexpensive means for displaying desired information. The device is simple, and the characters may be displayed in a shape that is natural to the observer. Also, the use of this single stroke method eliminates the possibility of the observer receiving false information. Whereas, in the seven, nine or fourteen bar or stroke method it is possible for one of the segments not to illuminate and the observer would not be aware of this fact. In addition, the use of multilayer circuits to electrically interconnect the character electrode segments eliminates the need for expensive encoding equipment and, also, eliminates the needs for a multiple of drive circuits for each segment of the character. Since each of the characters lie in the same plane, one voltage source may be used for all of the characters whereby each character is illuminated with the same degree of intensity.

As seen the concept set forth in this application has an unlimited field of application. It can be used as a display of numbers, etc. in equipment, for example, to present coded information on a pilots control panel of an airplane and many other applications.

While the above description relates to specific principles of this invention, it is to be understood that this description is made only by way of example and not as a limitation thereon for one skilled in the art may make modifications thereto but still be within the true spirit and scope of this invention as set forth in the appended claims.

What I claim:

1. An electroluminescent display device, comprising:

a substrate,

a transparent electrode in a plane substantially parallel to said substrate, and

an electroluminescent phosphor layer disposed between said transparent electrode and said substrate, said substrate including at least one character unit, said character unit having at least first and second preformed character electrodes, each character electrode assuming the configuration of a character to be illuminated, said character electrodes being interspersed amongst each other such that said character electrodes lie in the same plane, and occupy in part the same area within said character unit.

2. An electroluminescent display device as defined in claim 1, in which each of said character electrodes is composed of a plurality of individual segments having spaces therebetween.

3. An electroluminescent display device as defined in claim 2, in which the space between each of said segments of one of said character electrodes is occupied by a segment of another of said character electrodes within said character unit.

4. An electroluminescent display device as defined in claim 2, further including means for integrally electrically connecting each of said segments of said character electrodes so as to form one distinctive illuminated permanent character when a voltage is applied between said electrical connecting means and said transparent electrode.

5. An electroluminescent display device as defined in claim 4, in which said electrically connecting means includes a plurality of electrical circuit paths lying in planes substantially parallel to said character electrodes, each of said electrical circuit paths electrically coupling all the segments of a respective character electrode.

6. An electroluminescent display device as defined in claim 5, in which said electrical connecting means includes conductive members molecularly united to selected ones of said character electrode segments and extending substantially perpendicular thereto, said conductive members being molecularly united to selected ones of the electrical circuit paths in said substrate, said conductive members, said electrical circuit paths and said character electrode segments forming one integral unit.

7. An electroluminescent display device as defined in claim 6, in which said united conductive members and said electrical circuit paths are formed from an identical copper layer.

8. An electroluminescent display device as defined in claim 2, in which each of said character electrode segments forms a part of only one of said character electrodes in said unit.

9. An electroluminescent display device as defined in claim 1, further including a cover coating adjacent to and over said transparent electrode, said cover coating being coterminous with said transparent electrode.

10. An electroluminescent display device as defined in claim 1, in which said character units include a plurality of printed circuit character electrodes.

11. An electroluminescent display device as defined in claim 1, further including a dielectric layer disposed between said phosphor layer and said substrate.

12. An electroluminescent display device as defined in claim 1, further including means for facilitating connections of said character electrodes to external apparatus.

13. An electroluminescent display device, comprising:

a substrate,

a transparent electrode in a plane substantially parallel to said substrate, and

an electroluminescent phosphor layer disposed between said transparent electrode and said substrate,

said substrate including at least one character unit,

said character unit having a plurality of preformed character electrodes, each of said character electrodes including a series of spaced segments electrically interconnected to form the desired character when a voltage is im pressed between said segments and said transparent electrode, each of said segments forming a part of only one of said character electrodes with said character electrodes all lying in the same plane.

14. An electroluminescent display device as defined in claim 13, in which the space between each of said segments of one of said character electrodes is occupied by said segment of another of said character electrodes.

15. An electroluminescent display device is defined in claim 13, further including:

means for electrically connecting the segments of a character electrode,

said electrical interconnecting means including conductive members molecularly united to selected ones of said electrode segments, said conductive members extending substantially perpendicular to said electrode segments through said substrate, and

printed circuit paths, said conductive members being molecularly united to selected ones of the printed circuit paths in said substrate, said conductive mem- ,bers, said printed circuit paths, and said electrode segment forming one integral unit.

16. An electroluminescent display device as defined in claim 13, further including a cover coating adjacent to and over said transparent electrode and coterminous therewith.

' 17. An electroluminescent display device as defined in claim 13, in whichsaid character unit includes a plurality of printed circuit character electrodes.

18. An electroluminescent display device as defined in claim 13, further including a dielectric layer disposed between said phosphor layer and said substrate.

19. An electroluminescent display device as defined in claim 13, further including means for facilitating connections of said character electrodes to external apparatus. 7

References Cited UNITED STATES PATENTS HAROLD I. YPITTS, Primary Examiner US. Cl. X.R. 340366, 378 

